It should be local heating; you can do the same with a red laser pointer (or
any bright light with less energy then blue light). It is particularly cool
to use an IR laser pointer, or an IR led light to heat the glowing paper;
you can see the paper get bright as you force the paper to give up it's
energy, then it goes dark. Friction will heat the surface enough too, but
an IR laser pointer is a step up on the coolness scale.

Similarly, cooling the paper will cause the paper to get darker, and there
is less thermal energy allowing the molecules to de-excite. You can do this
with a piece of ice, but you can also take it a step further. If you cool
most glow in the dark papers in LN2, they will stop glowing, and will
fluoresce instead. The phosphorescent energy loss mode becomes unavailable,
and so the paper actually stores energy. Then, when you warm the paper up,
the molecules can begin to phosphoresce, and the paper will light up again.
if kept chilled, the paper will hold onto it's stored energy for hours, if
not longer.

It should be local heating; you can do the same with a red laser pointer (o=
r any bright light with less energy then blue light).=A0 It is particularly=
cool to use an IR laser pointer, or an IR led light to heat the glowing pa=
per; you can see the paper get bright as you force the paper to give up it&=
#39;s energy, then it goes dark.=A0 Friction will heat the surface enough t=
oo, but an IR laser pointer is a step up on the coolness scale.

Similarly, cooling the paper will cause the paper to get darker, and th=
ere is less thermal energy allowing the molecules to de-excite.=A0 You can =
do this with a piece of ice, but you can also take it a step further.=A0 If=
you cool most glow in the dark papers in LN2, they will stop glowing, and =
will fluoresce instead.=A0 The phosphorescent energy loss mode becomes unav=
ailable, and so the paper actually stores energy.=A0 Then, when you warm th=
e paper up, the molecules can begin to phosphoresce, and the paper will lig=
ht up again.=A0 if kept chilled, the paper will hold onto it's stored e=
nergy for hours, if not longer.

It might be from local heating. =A0Does red light work the same? =A0Try pla=
cing your hand on the surface for a few seconds. =A0The higher temperature =
leaves a bright handprint. =A0Lots of physics demo possibilities there.